1. Field
The following description relates to optical communications, and more particularly, to optical pumping.
2. Description of the Related Art
As an attempt to increase the capacity of an optical transmission link whose bandwidth is saturated, space-division-multiplexed optical transmission techniques have been studied. As one of the methods, the mode-division-multiplexed optical transmission which uses a few-mode fiber (FMF) as an optical link has been researched. A few-mode fiber has a single core and supports a number of modes, and an individual signal is transmitted through each mode, thus making it possible to increase the transport capacity in accordance with the number of modes supported by the FMF. For long-distance optical transmission using mode-division multiplexing, a few-mode fiber amplifier is required to amplify an optical signal that is attenuated while propagating along an optical link.